Anion-exchange properties of composite ceramic membranes containing hydrated zirconium dioxide

Composite membranes consisting of an inert ceramic matrix based on aluminum and zirconium oxides and of an ion-exchange component, hydrated zirconium dioxide, were prepared. The selectivity of these membranes to Cl^? ions was studied.     

Improving the interfacial property of carbon fiber/PI resin composite by grafting modification of carbon fiber surface

The poor interfacial adhesion between carbon fibers (CFs) and polyimide (PI) resin has seriously hampered the application of CF/PI composites. In this work, the interfacial adhesion was efficiently enhanced by grafting on the CF surface. Surface morphology and surface composition of modified carbon fibers were characterized, which indicated that acrylamide was grafted successfully on the CF surface and the surface roughness was increased slightly. After grafting, the interface shear strength of modified carbon fibers/PI composites was significantly improved by 86.96%, and the interlaminar shear strength was enhanced by 55.61% due to the covalent bonds in interphase and the toughening effect of sizing agent. Moreover, the mechanical properties of composites with different interfacial adhesion were measured, which further confirmed the effect of the grafting modification.     

Preparation and properties of polyimide/chopped carbon fiber composite foams

In this study, a series of reinforced polyimide (PI)/carbon fiber (CF) composite foams were fabricated through thermal foaming of polyester ammonium salt (PEAS) precursor powders. The PEAS precursor powders containing different contents of chopped CF were synthesized from benzophenone‐3,3′,4,4′‐tetracarboxylic dianhydride (BTDA) and 4,4′‐diaminodiphenyl ether (ODA). The effects of different CF loadings on foaming behavior of PEAS/CF composite precursor powders, final cellular morphology, and physical properties of PI composite foams were investigated. The results revealed that the chopped CF acted as nucleation agent in the foaming process. The dispersion of CF can be evaluated using digital microscope. It is interesting to find that the chopped CF were highly oriented along the direction of cell arrises. As a result, the mechanical properties of PI foams were significantly enhanced owing to the incorporation of chopped CF. Furthermore, the thermal stability of PI composite foams were also slightly improved owing to fine dispersion of CF. In addition, the PI/CF composite foam shows uniform cell size distribution and the best comprehensive physical properties as chopped CF loading at around 6 wt%. Copyright © 2016 John Wiley & Sons, Ltd.     

Viscoelastic characterization of phenolic resin–carbon fiber composite degradation process

Viscoelastic characteristics of cured phenolic resin–carbon fiber composite materials were investigated through glass transition and degradation reaction processes in the high‐temperature region up to 400°C. A typical glass transition of the crosslinked thermoset polymer was followed by irreversible degradation reactions, which were exhibited by the increasing storage modulus and loss modulus peak. A degradation master curve was constructed by using the vertical and horizontal shift factors, both of which complied well with the Arrhenius equation in light of the kinetic expression of degradation rate constants. Using an analogy to the Havriliak–Negami equation in dielectric relaxation phenomena, a viscoelastic modeling methodology was developed to characterize the frequency‐ and temperature‐dependent complex moduli of the degrading thermoset polymer composite systems. The temperature‐dependent relaxation time of the degrading composites was determined in a continuous fashion and showed a minimum relaxation time between the glass transition and degradation reaction regions. The capability of the developed modeling methodology was demonstrated by describing the complex behavior of the viscoelastic complex moduli of reacting phenolic resin composite systems. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 907–918, 1999     

Alder‐ene polymers derived from allyl aralkyl phenolic resin and bismaleimides: carbon fiber composites properties

The influence of structural variations in bismaleimides (BMIs) on Alder‐ene polymerization of O‐allyl aralkyl phenolic resin [O‐allyl Xylok (OAX)] was examined. Toward this, three BMI functional monomers, viz. 2,2′‐bis 4‐[(4′‐maleimido phenoxy) phenyl] propane (BMIP), 4,4′‐Bismaleimido diphenyl methane (BMPM), and Bis 4‐maleimidodiphenyl ether (BMPE), were blended with OAX in different molar ratios. The cure characterization revealed that the allyl‐dominated blends cure by three distinct reaction steps whereas the maleimide‐dominated blends exhibit a two‐step reaction invariable with the maleimide structure. Introduction of more maleimide functionalities increased the T_g and thermal stability of the co‐cured network. Differences in the storage modulus values and T_g of the BMI/OAX systems were correlated to the chemical structure of the BMI and crosslink density. Flexural, interlaminar shear strength (ILSS), and impact strength of the composites decreased systematically with the increase in maleimide content in the blend. Among the BMIs studied, T_g, thermal stability, and ILSS retention at elevated temperature were superior for BMPM/OAX blend owing to their high crosslink density and rigid backbone of the system. Allyl‐rich compositions exhibited improved mechanical properties owing to the better resin–reinforcement interaction as revealed from morphological analysis by scanning electron microscopy. Copyright © 2016 John Wiley & Sons, Ltd.     

Electrical detection of deoxyribonucleic acid hybridization based on carbon-nanotubes/nano zirconium dioxide/chitosan-modified electrodes

A novel and sensitive electrochemical DNA biosensor based on nanoparticles ZrO₂ and multi-walled carbon nanotubes (MWNTs) for DNA immobilization and enhanced hybridization detection is described. The MWNTs/nano ZrO₂/chitosan-modified glassy carbon electrode (GCE) was fabricated and oligonucleotides were immobilized to the GCE. The hybridization reaction on the electrode was monitored by differential pulse voltammetry (DPV) analysis using electroactive daunomycin as an indicator. Compared with previous DNA sensors with oligonucleotides directly incorporated on carbon electrodes, this carbon nanotube-based assay with its large surface area and good charge-transport characteristics increased DNA attachment quantity and complementary DNA detection sensitivity. The response signal increases linearly with the increase of the logarithm of the target DNA concentration in the range of 1.49 × 10⁻¹⁰ to 9.32 × 10⁻⁸ mol L⁻¹ with the detection limit of 7.5 × 10⁻¹¹ mol L⁻¹ (S/N = 3). The linear regression equation is I = 32.62 + 3.037 log C_DNA (mol L⁻¹) with a correlation coefficient value of 0.9842. This is the first application of carbon nanotubes combined with nano ZrO₂ to the fabrication of an electrochemical DNA biosensor with a favorable performance for the rapid detection of specific hybridization.     

The chlorination kinetics of zirconium dioxide mixed with carbon black

In this research, the effects of chlorine gas at different chlorine partial pressures and carbon concentrations on the carbochlorination of zirconia were studied. It was found that in briquettes containing 18.7 %wt carbon, in a chlorine partial pressure range of 0.25–0.75 atm and for a reacted fraction of less than 0.7, the chemical reaction model was dominant for the carbochlorination process of zirconia. The order of reaction into chlorine gas (n) in this situation was 0.57. Moreover, the best weight ratio of carbon to zirconia was 40/60. In this case, the activation energy of the reaction was 209.9 kJ mol^?1 in a temperature range of 1023–1223 K, and the dominant model was the chemical reaction model.     

Adsorption properties and photocatalytic activity of TiO2/activated carbon fiber composite

Photocatalysts of titanium dioxide (TiO₂) and TiO₂/activated carbon fiber (TiO₂/ACF) composite were prepared by sol-gel method, followed by calcining the pure TiO₂ sols and the TiO₂/ACF sols at 500°C for 2 h in a N₂ atmosphere, respectively. These photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and N₂ adsorption-desorption isotherms measurement. Batch experiments were conducted to study the adsorption property of TiO₂/ACF composite using methylene blue as adsorbate. The adsorption data obtained from different batch experiments were analyzed using pseudo-second-order kinetic model, the experimental data can be adequately described by the pseudo-second-order equation. The photodecomposition behavior of TiO₂/ACF was investigated in aqueous solution using methylene blue as target pollutant. It was found that methylene blue could be removed rapidly from water by TiO₂/ACF, the photocatalytic decomposition was obviously improved when the photocatalyst was used. Kinetics analysis revealed that the photocatalytic decomposition reaction can be described well by a first-order rate equation.     

Synthesis of TiC-C fiber from titanium isopropoxide treated phenolic resin fiber

Precursor fibers for titanium carbide-carbon fibers were synthesized by reacting phenolic resin fibers with titanium isopropoxide (TIP). In this system, titanium oxide gel coated fiber was prepared by hydrolyzing TIP infiltrated resin fiber. The precursor fibers obtained after the hydrolysis were converted into titanium oxide-carbon fibers (TiO₂-C fibers) by pyrolysis at 1273 K. The TiO₂-C fibers were converted into titanium carbide-carbon fibers (TiC-C fibers) by heat treatment at 1373–1973 K. The mechanisms of the conversion from TiO₂-C fibers to TiC-C fibers were characterized by TGA.     

Aerosol assisted synthesis of silica/phenolic resin composite mesoporous hollow spheres

Hollow spheres of phenolic resin/silica composite are synthesized by macroscopic phase separation of a sorbitan monooleate surfactant Span 80 during aerosol-assisted spraying. The cavity can be evolved from multiple compartments to single hollow cavity with the increase of Span 80 content. The composite shell becomes mesoporous due to the release of small molecules after thermal treatment above 350 °C. After further thermal treatment at a higher temperature for example 900 °C in nitrogen or 1,450 °C in argon, the carbon/silica composite hollow spheres or crystalline silicon carbide hollow spheres are derived, respectively. Compared to the pure phenolic resin-based carbon spheres, thermal stability of the carbon-based composite spheres in air is essentially improved by the introduction of inorganic component silica. The carbon-based composite hollow spheres combine both performances of easy mass transportation through macropores and high specific surface area of mesopores, which will be promising to support catalysts for fuel cells. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Photocatalytic oxidation of arsenite by a composite of titanium dioxide and activated carbon fiber

Preoxidation process is usually needed in the treatment of arsenic-containing drinking water because arsenite (i.e. As[III]) is less easily removed by adsorption. Nano-scale titanium dioxide is an efficient photocatalyst for arsenite oxidation but its application in water treatment is limited due to the difficulty of separation or packed-bed application of the tiny particles. This study synthesized a composite photocatalyst by loading titanium dioxide onto activated carbon fiber (TiO₂/ACF). The effects of calcination temperature, photocatalyst dosage, pH, initial concentration of As(III) and common anions on the oxidation of As(III) were studied. Photocatalytic oxidation of As(III) took place in minutes and followed first-order kinetics. 0.80 mg L⁻¹ of As(III) could be entirely oxidized to As(V) within 30 min in the presence of 3.0 g L⁻¹ photocatalyst and under UV-light irradiation. The oxidation of As(III) occurred in a wide range of pH as examined from 2 to 10 with the oxidation efficiency increasing markedly with pH. The presence of phosphate and silicate significantly decreased As(III) oxidation at pH 7, while the effect of sulfate and chloride was small.     

Grass fiber reinforced phenol formaldehyde resin composite: preparation,characterization and evaluation of properties of composite

There is a growing interest in the development of new materials through utilization of natural resources. This paper describes evaluation of water leached and alkali treated chopped grass fiber reinforced phenol formaldehyde composite. Here alkali treatment of grass fiber was carried out by varying the concentration of sodium hydroxide. The thermal stability of the composite was assessed by thermogravimetric analysis (TGA). Fourier transformation infrared spectroscopic study of both water leached and alkali treated grass fiber‐phenolic resin composite was also performed. Water absorption and swelling behavior of grass fiber phenolic resin composites in water were studied and the alkali treated grass fiber‐resin composite showed less water absorption and swelling. A composite prepared from 1% alkali treated grass fiber and 55% resin, showed the highest tensile strength whereas a composite prepared from 5% alkali treated grass fiber and 55% resin, showed maximum flexural properties. Copyright © 2006 John Wiley & Sons, Ltd.     

Effect of carbon fiber surface functionality on the moisture absorption behavior of carbon fiber/epoxy resin composites

Polyacrylonitrile (PAN)‐based carbon fibers were electrochemically oxidized in aqueous ammonium bicarbonate with increasing current density. The electrochemical treatment led to significant changes of surface physical properties and chemical structures. The oxidized fibers showed much cleaner surfaces and increased levels of oxygen functionalities. However, it was found that there was no correlation between surface roughness and the fiber/resin bond strength, i.e. mechanical interlocking did not play a major role in fiber/resin adhesion. Increases in surface chemical functionality resulted in improved fiber/resin bonding and increased interlaminar shear strength (ILSS) of carbon fiber reinforced epoxy composites. The relationship between fiber surface functionality and the hydrothermal aging behavior of carbon fiber/epoxy composites was investigated. The existence of free volume resulted from poor wetting of carbon fibers by the epoxy matrix and the interfacial chemical structure were the governing factors in the moisture absorption process of carbon fiber/epoxy composites. Copyright © 2016 John Wiley & Sons, Ltd.     

Synthesis and properties of a deuterated phenolic resin

A highly deuterated novolac‐type phenolic resin was prepared by polycondensation of deuterated phenol and formaldehyde using oxalic acid as an acid catalyst. The polycondensation of deuterated monomers and the formation of the highly deuterated phenolic resin were confirmed by the gel permeation chromatography, IR, and ¹H NMR analyses. With the exception of hydroxyl groups, the degree of deuteration was estimated to be more than 98%. The polymer conformation in THF solution was evaluated by the scaling exponent of the Mark–Houwink–Sakurada equation. The exponent of the deuterated phenolic resin is 0.26 in THF at 40 °C and is close to that of a nondeuterated phenolic resin, which suggests that phenolic resins behave like a compact sphere irrespective of deuteration. The curing behavior of the deuterated phenolic resin with hexamethylenetetramine was confirmed by differential scanning calorimetry analysis. The cured highly deuterated phenolic resin exhibits a lower incoherent neutron scattering background than that of the nondeuterated phenolic resin, which suggests that the former is suitable for matrix resins with low incoherent backgrounds for small‐angle neutron scattering studies of thermosetting resins. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011.     

Thermally stimulated creep study of bismaleimide/carbon fiber composite

The correlation between structure/microstructure and thermomechanical properties has been investigated by the Thermally Stimulated Creep (TSC) technique in a high performance thermostable thermoset matrix composite. The high resolving power of this technique allows us to analyse the retardation mode. The kinetics of molecular movements liberated at the glass transition has been investigated by the technique of fractional loading: the analysis of each elementary process gives the real compliance and the retardation time as a function of temperature. The values of the activation parameters show the existence of a compensation phenomenon which characterizes the microstructure. It also gives access to the loss compliance of the composite material as a function of temperature and frequency. The predictive calculation of loss compliance has been validated by the results obtained by dynamic mechanical analysis (DMA).     

Removal of iodate from aqueous solution using diatomite/nano titanium dioxide composite as adsorbent

Journal of Radioanalytical and Nuclear Chemistry - Highly deficient strontium cobaltite (SrCoOx), as a new nanomaterial that is thermally treated at low temperature...     

Separation of carbon dioxide/methane mixtures by adsorption on a basic resin

In this work, the separation of carbon dioxide/methane mixtures by PSA using a basic resin (Amberlite IRA-900) has been studied. Adsorption equilibrium and kinetics of carbon dioxide and methane on a fixed-bed of this adsorbent have been measured, and a binary adsorption equilibrium isotherm has been obtained. The adsorbent deactivation with the number of adsorption-desorption cycles, and its regeneration, have also been analysed. A model based on the LDF approximation has been used to describe the experimental breakthrough curves. The applicability of the basic resin to the separation of carbon dioxide/methane mixtures has been studied in an experimental PSA setup using a single bed. The validity of the model used in the fixed-bed study for simulating a PSA system has been checked by comparing the simulated and the experimental performance of the proposed PSA cycle.     

Effect of doping with small amounts of nickel on the catalytic properties of zirconium dioxide in the hydrogenation of carbon monoxide

Doping of zirconium dioxide with small amounts of nickel (0. 03 %) caused a several fold increase in the rate of formation of C₂-C₄ olefins, particularly isobutene, from CO and hydrogen. The combined catalyst ZrO₂-Ni/SiO₂ showed increased selectivity with respect to olefins in comparison with the Ni/SiO₂ catalyst.Science Prosp., 31. Translated from Teoreticheskiya i Éksperimental'naya Khimiya, Vol. 32, No. 6, 353–357, November-December, 1996. Original article submitted March 1, 1996.     

Improved interfacial properties of carbon fiber/UHMWPE composites through surface coating on carbon fiber surface

Carbon fibers were coated in an attempt to improve the interfacial properties between carbon fibers and ultra‐high molecular weight polyethylene resin matrix. Atomic force microscopy, scanning electron microscopy, and X‐ray photoelectron spectroscopy were performed to characterize the changes of carbon fiber surface. Atomic force microscopy results show that the coating of carbon fiber significantly increased the carbon fiber surface roughness. X‐ray photoelectron spectroscopy indicates that silicon containing functional groups obviously increased after modification. Interlaminar shear strength was used to characterize the interfacial properties of the composites.     

From superhydrophilicity to superhydrophobicity: the wetting behavior of a methylsilicone/phenolic resin/silica composite surface

A methylsilicone/phenolic resin/silica composite surface was prepared by a casting method. The wetting behavior of the surface was investigated. It was found that the as-prepared surface can be varied from superhydrophilicity to superhydrophobicity as the drying temperature increased. Methylsilicone/silica and phenolic resin/silica composite surfaces were also prepared as comparisons. Both of them cannot achieve superhydrophobicity. A mechanism was proposed to explain this phenomenon.